A decade after Gangster No 1 and Sexy Beast established them as the enfants terribles of British screenwriting, Louis Mellis and David Scinto are back, after a fashion. They broke up their writing partnership three years ago, but 44 Inch Chest, the last of their gangster triptych, written at the same time as the others, finally arrives in cinemas this month.

The story of its gestation is a ­cautionary tale that says much about the clannishness of the British film ­industry. Mellis and Scinto got stuck with a reputation for being wild, ­unnervingly close in character to their subjects. They first gained a reputation for combustibility when they walked off Gangster No 1 in a row over casting. The fact that Scinto was a former nightclub bouncer just added to their legend. "People told lies about us, and those lies were absorbed by the industry," says Scinto. "We got some kind of intimidating reputation which wasn't true. All we ever did was defend ourselves, and care about putting on a good show."

"Walking off Gangster No 1 was ­nightmarish," Mellis says. "When you're starting off, I guess you're supposed to be grateful. We did hear, almost: 'You'll never work in this town again.'"

Such were their frustrations that ­Mellis and Scinto, once the best of friends, stopped writing together in 2006. They now talk only rarely, though they live near each other in Brighton. Mellis is working on projects with ­Paramount and Jacques Audiard, but Scinto can't even get an agent. 44 Inch Chest was made largely without them, but remains unmistakably theirs.

"I can't think of any British writers working who have a unique voice in the way they do," says producer Jim Wilson, who oversaw Sexy Beast while working at FilmFour. "They have a vernacular they use, ­gangsterish and geezerish but more heightened and stylised. Yet as much as their scripts are about language, they are ­always reaching for visual storytelling. They are ­always asking: why is British cinema so ­uncinematic?"

Their main inspiration was painting. "Gangster No 1 was originally influenced by Bacon, Sexy Beast was Hockney, 44 Inch Chest was Magritte," Mellis says. "The gangster thing wasn't researched, or from ­speaking to cockney hardmen. We just got in a room and made ourselves laugh."

Mellis and Scinto scripts are famous for their precise directions. "We used to say that we'd already seen our films ­before we wrote them, it's just a process of getting down on paper what we'd seen," says Mellis. No wonder they were unwilling to bend to anyone else's ­vision, at whatever cost to themselves. Their agent at the time, Steve Kenis, says: "I've seen them walk away from money on the table when they didn't even have the bus fare home."

They also say they felt like outsiders to the British film club. "It's almost like they speak a different language from me," says Mellis. Both men are working-class autodidacts, who tried every job under the sun before they met at a party and wrote Gangster No 1, ­originally as a play. Jonathan Glazer was supposed to direct it, but they all quit together when the producer tried to cast Peter Bowles in the role that ­eventually went to Malcolm McDowell; the trio then poured their ­anger into ­creating Sexy Beast.

Hot in Hollywood after Sexy Beast, Mellis and Scinto undertook a string of American rewrite jobs that went ­nowhere. They wanted to direct 44 Inch Chest, but fell out instead. Mellis admits the split made them less possessive of their old work. "It was like selling off the family jewels. No point in them ­sitting in the drawer to die." And so ­another old script, Sssucker, is inching forward with Glazer.

Perhaps the next decade will be kinder than the last. The British film ­industry doesn't have so many great writers that it can afford to ignore them. "I'm older and wiser, I'll learn my ­lessons and make my film," says Scinto. "But it's a bit weird. I would have thought we would have received more support, but we got practically none in this country."